It will be attempted to produce monoclonal antibodies against allotype 7a and 7b, the two most important allotypes of murine IgE, the antibody responsible for anaphylactic reactions. Allotype 7b does not crossreact with any other allotype T antibodies and allotype 7a crossreacts with all the other allotype 7 antibodies except with allotype 7b. These two monoclonal antibodies (anti-7a and anti-7b) would be of great importance for research in experimental allergic reactions. For the production of these monoclonal antibodies the hybridoma technique will be used. Spleen cells from inbred mice immunized against allotype 7a or 7b and producing anti-7a or anti-7b antibodies will be fused with a nonproducing myeloma cell and the hybridoma cells obtained will be checked for the production of anti-7a or anti-7b monoclonal antibodies, using as test passive hemagglutination of sheep red blood cells coated with 7a or 7b IgE antibodies. T cells from inbred mice primed with well defined immunogenic antigens, will be cloned, using a standard method of T cell cloning. Long term cultures will be established from those cell lines which have specificity for the antigen demonstrated by radiolabeled thymidine incorporation. These T cell lines will be then tested in vitro for antigen specific help using primed B cells from inbred mice syngeneic to the mice from which the T cells were cloned. The B cells will be from mice primed with hapten-carrier protein complex, but the carrier protein will be different from that used to prime the T cells. In the in vitro tests the same hapten that was used for priming the B cells will be coupled to the antigen used for the T cells. In this way it will be possible to ascertain antigen specific help by the T cells and the role of these T cells in production of different murine isotypes, especially IgE antibody. T cells from SJA9 mice taken from mice infected with Nippostrongylus brasiliensis will be cloned on feeder cells from Nippostrongylus infected mice. It will be attempted to clone by this procedure the T cell which brings about the switch for IgE production in this strain. The cloned T cells will be tested in SJA9 mice in vivo and also with SJA9 spleen cells from primed mice in vitro.